[Solved] You created an index on the email column, but your query remains slow:SELECT * FROM users WHERE email LIKE '%example.com';What is the most probable reason? | SQL

SQL - Indexes and Query Performance

You created an index on the email column, but your query remains slow:

SELECT * FROM users WHERE email LIKE '%example.com';

What is the most probable reason?

AThe leading wildcard (%) prevents the index from being used

BThe index was created on the wrong column

CThe database does not support indexes

DThe query syntax is incorrect

Step-by-Step Solution

Solution:

Step 1: Understand index limitations
Indexes on text columns cannot be used efficiently when the search pattern starts with a wildcard.
Step 2: Analyze query pattern
The pattern '%example.com' has a leading wildcard, so the index on email cannot be used effectively.
Final Answer:
The leading wildcard (%) prevents the index from being used -> Option A
Quick Check:
Leading wildcards disable index usage [OK]

Quick Trick: Leading % in LIKE disables index use [OK]

Common Mistakes:

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